package com.iexbuy.ihg.utils;

import java.io.BufferedInputStream;
import java.io.ByteArrayOutputStream;
import java.io.FileInputStream;
import java.io.FilterOutputStream;
import java.io.IOException;
import java.io.OutputStream;
import java.io.UnsupportedEncodingException;

public class Base64Encoder extends FilterOutputStream {
	private static final char[] chars = {
	    'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J',
	    'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R', 'S', 'T',
	    'U', 'V', 'W', 'X', 'Y', 'Z', 'a', 'b', 'c', 'd',
	    'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n',
	    'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x',
	    'y', 'z', '0', '1', '2', '3', '4', '5', '6', '7',
	    '8', '9', '+', '/'
	  };

	  private int charCount;
	  private int carryOver;

	  /***
	   * Constructs a new Base64 encoder that writes output to the given
	   * OutputStream.
	   *
	   * @param out the output stream
	   */
	  public Base64Encoder(OutputStream out) {
	    super(out);
	  }

	  /***
	   * Writes the given byte to the output stream in an encoded form.
	   *
	   * @exception IOException if an I/O error occurs
	   */
	  public void write(int b) throws IOException {
	    // Take 24-bits from three octets, translate into four encoded chars
	    // Break lines at 76 chars
	    // If necessary, pad with 0 bits on the right at the end
	    // Use = signs as padding at the end to ensure encodedLength % 4 == 0

	    // Remove the sign bit,
	    // thanks to Christian Schweingruber <chrigu@lorraine.ch>
	    if (b < 0) {
	      b += 256;
	    }

	    // First byte use first six bits, save last two bits
	    if (charCount % 3 == 0) {
	      int lookup = b >> 2;
	      carryOver = b & 3;        // last two bits
	      out.write(chars[lookup]);
	    }
	    // Second byte use previous two bits and first four new bits,
	    // save last four bits
	    else if (charCount % 3 == 1) {
	      int lookup = ((carryOver << 4) + (b >> 4)) & 63;
	      carryOver = b & 15;       // last four bits
	      out.write(chars[lookup]);
	    }
	    // Third byte use previous four bits and first two new bits,
	    // then use last six new bits
	    else if (charCount % 3 == 2) {
	      int lookup = ((carryOver << 2) + (b >> 6)) & 63;
	      out.write(chars[lookup]);
	      lookup = b & 63;          // last six bits
	      out.write(chars[lookup]);
	      carryOver = 0;
	    }
	    charCount++;

	    // Add newline every 76 output chars (that's 57 input chars)
	    if (charCount % 57 == 0) {
	      out.write('\n');
	    }
	  }

	  /***
	   * Writes the given byte array to the output stream in an 
	   * encoded form.
	   *
	   * @param buf the data to be written
	   * @param off the start offset of the data
	   * @param len the length of the data
	   * @exception IOException if an I/O error occurs
	   */
	  public void write(byte[] buf, int off, int len) throws IOException {
	    // This could of course be optimized
	    for (int i = 0; i < len; i++) {
	      write(buf[off + i]);
	    }
	  }

	  /***
	   * Closes the stream, this MUST be called to ensure proper padding is
	   * written to the end of the output stream.
	   *
	   * @exception IOException if an I/O error occurs
	   */
	  public void close() throws IOException {
	    // Handle leftover bytes
	    if (charCount % 3 == 1) {  // one leftover
	      int lookup = (carryOver << 4) & 63;
	      out.write(chars[lookup]);
	      out.write('=');
	      out.write('=');
	    }
	    else if (charCount % 3 == 2) {  // two leftovers
	      int lookup = (carryOver << 2) & 63;
	      out.write(chars[lookup]);
	      out.write('=');
	    }
	    super.close();
	  }

	  /***
	   * Returns the encoded form of the given unencoded string.  The encoder
	   * uses the ISO-8859-1 (Latin-1) encoding to convert the string to bytes.
	   * For greater control over the encoding, encode the string to bytes
	   * yourself and use encode(byte[]).
	   *
	   * @param unencoded the string to encode
	   * @return the encoded form of the unencoded string
	   */
	  public static String encode(String unencoded) {
	    byte[] bytes = null;
	    try {
	      bytes = unencoded.getBytes("8859_1");
	    }
	    catch (UnsupportedEncodingException ignored) { }
	    return encode(bytes);
	  }

	  /***
	   * Returns the encoded form of the given unencoded string.
	   *
	   * @param bytes the bytes to encode
	   * @return the encoded form of the unencoded string
	   */
	  public static String encode(byte[] bytes) {
	    ByteArrayOutputStream out = 
	      new ByteArrayOutputStream((int) (bytes.length * 1.37));
	    Base64Encoder encodedOut = new Base64Encoder(out);
	    
	    try {
	      encodedOut.write(bytes);
	      encodedOut.close();

	      return out.toString("8859_1");
	    }
	    catch (IOException ignored) { return null; }
	  }

	  public static void main(String[] args) throws Exception {
	    if (args.length != 1) {
	      System.err.println(
	        "Usage: java com.oreilly.servlet.Base64Encoder fileToEncode");
	      return;
	    }

	    Base64Encoder encoder = null;
	    BufferedInputStream in = null;
	    try {
	      encoder = new Base64Encoder(System.out);
	      in = new BufferedInputStream(new FileInputStream(args[0]));

	      byte[] buf = new byte[4 * 1024];  // 4K buffer
	      int bytesRead;
	      while ((bytesRead = in.read(buf)) != -1) {
	        encoder.write(buf, 0, bytesRead);
	      }
	    }
	    finally {
	      if (in != null) in.close();
	      if (encoder != null) encoder.close();
	    }
	  }
}
